1. Science Form 2 note Teacher zaidi@maher2010
CHAPTER 2: NUTRITION
1. Living things need food to survive.
2. Food can divided into seven classes as follows:
i. carbohydrates
ii. proteins
iii. fats
iv. vitamins
v. minerals
vi. fibre
vii. water
Carbohydrate PMR 03 FOOD TEST
1. Carbohydrate is made up of carbon, hydrogen and oxygen.
2. There are three types of carbohydrate, starch, sugar and cellulose.
3. Carbohydrate are present in various forms, such as:
i. starch, which is stored in plants.(bread, potatoes)
ii. Sugars, which are sweet and soluble in water.
iii. Cellulose, which is found in plant cell walls and cannot be
digested.(vegetable and fruits)
iv. Glycogen, which is found in liver and muscles.
4. Food rich in carbohydrate include rice; potato, sugar, bread, and banana.
5. Carbohydrate is our main source of energy. Carbohydrate supplies us with
energy to carry out daily activities such as walking, breathing, and
working.
Protein PMR 03 FOOD TEST
1. Protein is made up of carbon, hydrogen, oxygen, and nitrogen.
2. Sometimes protein can also contain phosphorus and sulphur.
3. Food rich in protein includes fish, milk, meat, egg white and nuts
(groundnuts and soya bean). PMR 04
4. Proteins are required for building new cells for growth, to replace
damaged tissue.
2. Science Form 2 note Teacher zaidi@maher2010
5. Growing children require a lot of protein. Lack of protein will cause a
disease know as kwashiorkor (stunted growth).
Fat
1. Fat is made up for carbon, hydrogen and oxygen but the ratio is different
from that of carbohydrate.
2. Food rich in fats includes palm oil, butter and egg yolk.
3. Fat produces twice the amount of energy compared with carbohydrate of
the same weight.
4. The function of fat include:
a. supplying energy,
b. as and insulator of heat to reduce heat loss from the body,
c. protecting the internal organs such as the kidneys and the heart,
d. dissolving some vitamins in the body like vitamin A, D, E and K.
Vitamins
Go to www.exhibits.pacsi.org/nutrition play `nutrition sleuth’ and click `open the
case book’ to check what you know about nutrients.
1. Vitamins are required in small quantities only.
2. Vitamins are classified into two groups
a. vitamins soluble in water – vitamin B and C ,
b. vitamins soluble in fat- vitamin A, D, E and K.
3. Vitamins protect the body from various types of diseases and maintains the
health of the body.
Photostat m/s 42
3. Science Form 2 note Teacher zaidi@maher2010
Vitamin Main source Function Effect of deficiency
A
Egg, milk, cod liver,
oil, carrot, papaya
- for growth and to promote
healthy skin
- for good vision
- night blindness
- dry and scaly skin
B
yeast, egg, milk,
tomato, liver, nuts
- promotes the effective
functioning of the nervous
system
- control the supply of
carbohydrates to the muscle
and nerve cells
- beri-beri (injury to
the nervous system
and paralysis)
- pellagra
- anaemia
C
lime, citrus fruits,
tomato, carrot ,
papaya, green
vegetables
- increase immunity against
disease
- promotes healthy skin
- scurvy (gusi merah)
- anaemia
- low resistance to
infections (especially
the flu)
D egg, milk, cod liver oil
- helps in the absorption of
calcium and phosphorus in the
small intestines for the growth
of strong bones and teeth.
- rickets (weak and
curved bones)
- tooth decay
E
vegetable oil, palm oil,
egg, liver, milk
- maintains a healthy
reproductive system
- sterility
- infertility
K
maize, sunflower seeds,
tomato, green
vegetables
- necessary for the clotting of
blood.
- blood slow to clot
Minerals
1. minerals are simple chemicals usually found in the body.
2. our bodies need more calcium and phosphorus than the minerals.(because
they help to form strong bones and teeth)
3. minerals are needed for good health.
Photostat ms 44
4. Science Form 2 note Teacher zaidi@maher2010
Sources and functions of minerals as well as the effects of mineral deficiencies
Minerals sources of food Functions
effects of
deficiency
Calcium
milk, eggs,
vegetables, cheese
* forms strong bones
and teeth
* helps blood to colt
* rickets
* brittle
bones and
teeth
* poor blood
clotting
iron
liver,, meat, eggs,
vegetables
* forms haemoglobin
in red the thyroid
blood cells
* anaemia
iodine
seafood, vegetables,
iodinised salt
* produces hormones
in the thyroid gland
* Goitre
sodium common salt, * balances body fluid
* muscle
cramps
phosphorus
meat, milk, eggs,
beans
* forms strong bones
and teeth
* rickets
* dental
decay
fluorine
drinking water, fish,
vegetables
* protect teeth
* Dental
decay
potassium meat, fish, cereals
* maintains a
healthy nervous
system
* muscle
cramps
Fibre
1. Fibre is made up of cellulose which cannot be digested by the body.
2. A shortage of fibre in our daily diet can cause constipation and sometimes
even bowel cancer.
3. Vegetables, fruit, beans, lentils and brown bread are examples of food
rich in fibre.
Water
1. approximately 65% to 70% of a person’s body weight is made up of water.
2. The body obtains water when we drink water and also when we consume
fruits and vegetables.
5. Science Form 2 note Teacher zaidi@maher2010
3. Water is needed by the body for:
a. helping in the digestion of food
b. transporting digested food substances
c. transporting excretory products such as urea.
d. maintaining the concentration of blood.
e. maintaining the body temperature
f. all metabolic processes
FOOD TEST (experiment) PMR 03
The importance of a balanced diet
http://www.en.wikipedia.org/wiki/food_guide_pyramid
1. Diet refers to the food and drinks that we consume daily.
2. A balanced diet is one which contains carbohydrates, proteins, fats,
minerals, vitamins, water and fibre in the correct quantities and
proportions.
3. A balanced diet is necessary for:
a. supplying the required energy
b. balanced body growth
c. maintaining the health of the body
d. preventing deficiency diseases such as scurvy and rickets.
4. A balanced diet varies according to one’s
i. Age
ii. size
iii. sex
iv. job
v. climate
vi. state of health
6. Science Form 2 note Teacher zaidi@maher2010
Factors that influence a person’s needs for a balanced diet
Factors the group requiring more energy Reason
sex
men required more energy compared to
women of the same age and body size.
men are more active
age
babies, children and teenagers require
more energy compared to adults or the
elderly. Example: the heartbeat of baby
is 100 beats a minute compared to an
adult who has 75 beats per minute.
this group is more active and the
life processes are faster.
body size
big-size individuals require more energy
size compared to small-sized individuals.
big-sized individuals require more
energy for their life processes.
physical
activity
an individual who does heavy work uses
more energy compared to another who
does light work.
heavy work requires more energy
to perform.
weather
individuals living in places with cold
weather require more energy compared to
individuals living in places with warm
weather.
more energy is required to
maintain the body temperature in
a cold place.
The calorific value of food PMR 06, 07
1.. Energy in food measured in joules (J) or calories (cal).
1 calorie (cal) = 4.2 joules (J)
1 kilocalorie (kcal) = 4.2 kilojoules (kJ)
2. The calorific value of food is the amount of heat energy released when
one gram of food is completely burnt in the air.
3. The calorific value of food is measured in kilojoules per gram (kJ/g) or
kilocalories per gram (kcal/g)
4. The calorific value differs for different types of food. Table below shows
the calorific value of some of the food that we eat daily.
food type calorific value (kJ/g)
margarine 35.5
Cake 18.3
Rice 15.0
roti canai 13.3
7. Science Form 2 note Teacher zaidi@maher2010
fried noodles 13.0
chicken curry 7.8
Egg 6.8
banana 3.3
papaya 1.65
spinach 0.88
5. Table shows the results of surveys carried out on individuals according to
age, sex and profession.
Individual
energy in kJ
male Female
child, 8 years old 8800 8800
teenager, 15 years old 12600 9600
adult, clerk 11500 9450
adult, labourer 20000 12600
pregnant mother - 10000
lactating mother - 11300
HUMAN DIGESTIVE SYSTEM
http://www.teachnet.ie/farmnet/Digestive.htm
http://www.enchantedlearning.com/subjects/anatomy/digestive/
1. Digestion is the process of breaking down large and complex food substances
into smaller, simpler molecules. These molecules are soluble and can be
absorbed by body cells.
2. the digestive process occurs in a system which is called the digestive system.
3. Figure below shows the human digestive system
m/s 49 figure 2.8 (Photostat)
4. part of the digestive system and their function are shown below.
8. Science Form 2 note Teacher zaidi@maher2010
parts of the
digestive
tract
Functions
Mouth
• chew and grinds food using the teeth
• digests cooked starch. The amylase enzymes in the saliva
change cooked starch to maltose.
• The salivary glands secrete saliva which contains an enzyme
called amylase.
• Amylase digests starch and convert it to maltose (a type of
sugar)
Oesophagus
• bolus-shaped food is moved from the mouth to the stomach
along the oesophagus by wave-like muscular contractions called
peristalsis.
Stomach
PMR 03
• holds food, secretes gastric juices which begin the digestion of
protein
• secretes acids contains hydrochloric acid which kill the bacteria
in food.
Duodenum
• receives bile from the liver and pancreatic juice from the
pancreas.
• Digestion and absorption of food.
small
intestine
• secretes intestinal juice which completes the digestion of
protein, carbohydrates and fat.
• Absorbs end products of digestion into the blood.
large
intestine
• absorption of most of the remaining water and minerals.
Rectum • stores faeces
Anus • removes faeces through defecation.
6. The process of digestion in the alimentary canal:
a. physical digestion - involves the mechanical process of
breaking down large pieces of food
into smaller particles using the teeth
and the churning movements of the
alimentary canal.
b. chemical digestion - involves the action of various
9. Science Form 2 note Teacher zaidi@maher2010
enzymes in breaking down complex
food molecules. These complex
molecules are insoluble but the end
products of chemicals digestion are
simpler molecules which are soluble.
7. Flow of food particles in the alimentary canal:
Go to www.kidshealth.org/kid/body/mybody_SW.html click on `digestive system’
for a tour through your food tube.
For easy access, go to www.icd.com.my
a. mouth
i. Digestion begins in the mouth.
ii. The teeth chew and grind food into smaller particles.
iii. the salivary glands secrete glands secrete saliva which contains an
enzyme called amylase.
iv. Amylase digests starch and converts it to maltose, a type of sugar.
v. The wave-like contractions of the oesophagus muscles are known as
peristalsis.
Draw figure 2.10 page 50
b. stomach
i. in the stomach, food is mixed with gastric juices. Gastric
glands in the stomach wall.
ii. Gastric juices contains hydrochloric acid and enzymes (rennin and
pepsin) .
iii. The functions of hydrochloric acid include:
a. Hydrochloric acid stops the action of the enzymes in saliva.
b. It also kills bacteria in food.
iv. Enzymes in the gastric juices start the digestion of protein.
Example:
a. pepsin digests protein into peptones.
10. Science Form 2 note Teacher zaidi@maher2010
pepsin
Protein peptones
b. Rennin coagulates milk in the stomach to help in the enzymic
action of pepsin.
rennin
Liquid milk proteins solid milk proteins
v. Partially digested food is then released into the duodenum.
c. small intestine
i. The duodenum is the first parts of the small intestine.
ii. The duodenum receives bile and pancreatic juice. (bile is stored in
the gall bladder)
iii. The function of bile:
a. Emulsifications of fat i.e. breaking up large fatty globules
into small droplets for enzymic action.
b. Preparation of an alkaline medium for enzymic action.
iv. The pancreatic amylase digests starch into maltose.
v. The protease digests protein/peptones into amino acids.
vi. The lipase digests fat into fatty acid and glycerol.
vii. The small intestine (ileum) produces enzymes which digest maltose
into glucose (simple sugar)
viii. Digestion is completed in the small intestine.
ix. The digested food is then ready to be absorbed through the thin
walls of the small intestine into the bloodstream.
SUMMARY OF PROCESS OF CHEMICAL DIGESTION IN
THE HUMAN ALIMENTARY CANAL
Absorption of the products of digestion
1. Absorption is the process when the end products of digestion enters the
bloodstream through the small intestinal walls.
11. Science Form 2 note Teacher zaidi@maher2010
2. The inner surface of the small intestine (6 metres long) covered with
millions of small projections about 1mm long. These projections are called
villi @ villus.
3. Food that has been digested into its most simple form is absorbed by the
villi @ villus on the small intestinal walls into the bloodstream.
4. The efficiency of absorption of digested food at the small intestine can
be increased by:
a. more villus to increase surface area
b. villus with very thin walls
5. Each villus has a network of a blood capillaries and a lacteal.
6. Glucose, amino acids, minerals and water-solube vitamins are absorbed
into the blood capillaries.
7. Fatty acids, glycerol and fat-soluble vitamins (vitamin A, D, E and K) are
absorbed into the lacteal.
lukis rajah m/s 52 figure 2.13
REABSORPTION OF WATER AND DEFACATION
Go to www.innerbody.com/htm/body.html move over the image of digestive
system’ and then click on the eyeglasses at the ascending colon.
Reabsorption of water
1. The main function of big intestine is to reabsorb water.
2. The substances that enter the big intestine consist of water and
undigested food substances like cellulose from the fibre of vegetables
and fruits (roughage)
3. Water is reabsorbed from these undigested food substances.
4. Undigested food materials together with water is passed to the colon
(first part of the large intestine)rectum is the last portion of the large intestine
http://www.abbysenior.com/biology/digestive_system.htm
12. Science Form 2 note Teacher zaidi@maher2010
Defecation
1. Undigested food in the big intestine is expelled as faeces through the
process of defecation.
2. When the rectum is full of faeces, the rectum undergoes peristalsis and
assisted by abdominal contraction, will push the faeces through the anus
to be expelled.
3. If an individual has problems passing motion, he or she is said to be
constipated.
4. Constipation takes place because of the lack of water in the diet.
Lukis rajah m/s 53 figure 2.15
Lihat Microsoft power point
HEALTHY EATING HABITS
The food pyramid PMR 05, 08
http://www.east-buc.k12.ia.us/04_05/655/bs/bs.htm
http://www.pediatric-orthopedics.com/Topics/Bow_Legs/bow_Legs.html
1. Healthy eating habits will help maintain a healthy body.
2. Unhealthy eating habits cause various health problems.
1. excessive nutrient health problems
Sugar tooth decay, obesity, diabetes
Salt high blood pressure, heart problems,
kidney damage
fat/oil heart problems, high blood pressure
2. lack of nutrient health problems
Protein kwashiorkor in children
Roughage Constipation
Vitamins lower immunity to diseases
